JPH02501934A - Separation method and plant for synthetic water-soluble polymers - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Method and plant for separating synthetic water-soluble polymers The present invention is a method for separating synthetic water-soluble polymers by filtering them. Separate into two types of solutions by filtration process, and use the IN solution for repolymerization. Regarding how to recirculate. The present invention also relates to a polymerization reactor and the resulting synthetic water-soluble polymer. limmer separation equipment.

Natural polymers such as proteins, natural rubber latex, and cellulose are often highly It has a well-defined molecular weight. In contrast, synthetic polymers are typically With a wide molecular weight distribution, often only fractions containing high molecular weight polymers are planned. It has good properties desirable for applications. In order to obtain only the desired high molecular weight fraction, Therefore, it is always possible to control polymer synthesis with available technologies. is not limited. Synthesized resins contain undesirable low molecular weight polymers and by-products. In addition, unreacted monomers are often present.

The present invention provides synthetic water-soluble polymers for obtaining preferred high molecular weight fractions with advantageous properties. The method provides a method for the separation of polymers, which further recycles the low molecular weight fraction to the polymerization process. It also includes.

The molecular weight of synthetic polymers depends on, for example, the monomers, the type of polymer reaction, reaction time, and temperature. It depends on several variables such as temperature. For polymers in solution, the molecular weight distribution is almost always has a curved shape. This curve will of course vary from polymer to polymer and will include more than one piston. has a network. For example, water-soluble urea-formaldehyde resins have two clearly defined It has been found that the molecular weight distribution includes specific peaks.

According to the method of the invention, preferred high molecular weight fractions of such resins can be reused. It can be separated from undesirable fractions.

The method of the invention is generally applicable to the separation of preferred high molecular weight fractions of water-soluble synthetic resins. It is Noh. However, this method is especially advantageous for water-soluble resins used in papermaking. , the following invention may apply to such resins, although it is not limited thereto.

Examples of water-soluble resins used in papermaking include urea-formaldehyde resin and melamine-formaldehyde resin. maldehyde resin and polyamidoamine-shrimp chlorohydrin. these Resins are used as wet strength agents for paper, and their effect on wet strength is highly It has been found that it can only be obtained by molecular fractionation. The low molecular weight fraction is retained on paper. It is circulated in a closed white water system. Formaldehyde-based resins have high Hot water reduces the hydrolysis of this low molecular weight fraction and the release of free phosphates that can pose environmental problems. This results in the release of lumaldehyde. Polyamidoamine-shrimp chlorohydrin resin has a higher molecular weight than formaldehyde-based resins, and the lower molecular weight fraction of this resin Painting has only a low effect on wet strength. Additionally, these resins are environmentally friendly. It contains monomer chlorination by-products which also cause problems.

When the above resin is treated by the method of the present invention, an aqueous solution of a high molecular weight polymer is obtained. It has a very good wet strength effect and is suitable for use in water and air in paper mills. of formaldehyde and other undesirable compounds.

Urea-formaldehyde resins are the primary wet strength resins, but they pose significant environmental problems. These improvements according to the present invention are particularly important as these resins are also prone to Therefore, these resins will be discussed in more detail below.

As mentioned above, during paper manufacturing, urea-formaldehyde resin is processed by hydrolysis. Free formaldehyde is released. Additionally, the first resin used is also always free. Contains formaldehyde, which accumulates and circulates in the white water system.

All the concentrated solutions obtained by the separation according to the invention are much better compared to the starting resin. The amount of addition necessary to obtain a certain wet strength effect is small. decrease. In the concentrated solution there is more unreacted monomer (e.g. The content of formaldehyde) and low molecular weight by-products is also low, which makes it suitable for white water systems. Unsatisfactory products are doubly degraded. - As an example, the first formaldehyde resin contains 7% free formaldehyde on a resin dry weight basis, which can be reduced by the method of the present invention. A concentrated solution of the same urea-formaldehyde resin obtained by do not have. The amount of urea-formaldehyde resin usually added during papermaking is 10 per ton of paper. ~24 kg. With the concentrate of the present invention, only 6-12 kg dry weight of resin The same wet strength effect can be obtained by This means that “added free formaldehyde Cg decreases from 0.7 to 1.4) Cg to 0.24 to 0.48 kg. i.e. This means that a reduction of 80-70% occurs.

This reduction is due to the fact that the concentrate contains only a small amount of easily hydrolyzed low molecular weight resin. It is further strengthened by the fact that there is no such thing. Similarly, the sulfur content in the monomer Anionic minerals found to contain approximately 1/2 of formaldehyde Bisulfate modified urea-formaldehyde resins are also treated by the method of the invention to Besides having no wet strength effect, the 2-potential (Z-potential) of the stock al) can be removed. in this way , urea-formaldehyde resin and melamine-formaldehyde resin. Using the method of the present invention to separate molecular weight fractions produces effective wet strength resin products. products that not only form but also are advantageous from an environmental and occupational point of view It also brings.

The method of the present invention further comprises using a solution of low molecular weight compounds obtained during separation for repolymerization. including recycling.

This recycling for repolymerization is preferably carried out after the reforming step. The present invention is Furthermore, it is possible to produce a preferred high molecular weight fraction of water-soluble synthetic polymers while simultaneously producing a low molecular weight fraction. Enables reuse of images. Provide a technically and commercially advantageous method.

According to the present invention, a feed aqueous solution of a water-soluble synthetic resin is charged into an ultrafiltration membrane device; The device feeds the solution into two types of solutions, i.e. mainly polymer molecules with high molecular weight. and permeate containing low molecular weight polymer molecules, monomers and by-products. The permeate is then recycled to the polymerization process.

Ultrafiltration equipment requires an appropriate cutoff to retain the desired high molecular weight fraction. These membranes are tailored by specific polymers and preferred fractions. It changes naturally. Suitable types of membranes include, for example, polysulfone, cellulose acetate, polymer Lyamide, vinyl chloride-acrylonitrile copolymer and poly(vinyl fluoride) Liden) membrane. This membrane device can be used, for example, in a plate/frame module (pla (te-and-flame modules), but other types of membranes Of course, the device can also be used. The actual resin to be separated before separation is applied to this membrane. Pretreatment with a dilute solution is suitably carried out. This pretreatment helps form the second film layer. stand. For urea-formaldehyde resins, the preferred high molecular weight fraction is 2000-40 00 and the fraction is treated as a membrane-retained component, i.e., as a concentrate or a retentate. It is carried out in such a way that it essentially gives. For this purpose, 20,000 to 200,000 As a guideline, we will state that the above types of membranes with cut-off properties are appropriately used. be able to. Other resins include carbon fibers within the range of 200,000 to 400,000. Membranes with to-off can generally be used.

The dry content of the feed solution to the ultrafiltration device is usually in the range 8-25% by weight. Should. The process is generally carried out at a pressure of about 1.0-15 bar and is passed through a membrane. The flow rate increases with increasing temperature. However, the selected temperature may cause the resin or membrane to Care must be taken to ensure that it is not harmful. Membranes of the above type and e.g. urea - formaldehyde, melamine - formaldehyde and polyaminopolyamide For separation of epichlorohydrin resin, temperatures within the range of 30-45°C are used. It is appropriate to be there.

Concentrate from the membrane unit is recycled to the membrane unit via a feed tank until the desired concentration is reached. It is advantageous to carry out the filtration in several passes through the membrane device until obtained. child Alternatively, it is also natural to carry out continuous treatment of the concentrate with several membrane devices. It is possible.

Contains low molecular weight polymers obtained from the ultrafiltration device, hereinafter referred to as UF permeate. The aqueous solution, filtrate or permeate, is returned to the first resin polymerization reactor for repolymerization. to form an economical process that does not result in material loss.

The separation in the ultrafiltration device is based on the initial dry resin content, i.e. high and low molecular weight polymers. The procedure is such that at least 5% by weight of the reamer fraction is separated into the permeate solution. preferable. Depending on the amount of substance separated in the permeate solution and the associated amount of water, A modification step of the UF-permeate can be included before recycling to the polymerization reactor. child If the amount of It can also be carried into polymerization. Otherwise, make sure there is not too much water left in the polymerization-separation system. This also avoids the accumulation of unacceptable amounts of undesirable products in the system. As such, it is appropriate to carry out the modification of the UF-permeate in accordance with the preferred embodiment of the present invention. According to Improved to remove at least part of. This improvement can be achieved by e.g. evaporation or This can be carried out by conventional reverse osmosis membrane filtration. Reverse osmosis process is relatively inexpensive is advantageous in that the thermal load on the polymeric substances in the UF-permeate is low. Therefore, it is preferable to carry out this improvement by reverse osmosis. The reverse osmosis process is This results in unreacted additives and by-products (e.g. formaldehyde). It is also advantageous in terms of separation. Concentrated UF obtained by reverse osmosis - permeate is resin used in the synthesis of fluorine and recycled for repolymerization, but passed through the membrane of a reverse osmosis device. The solution, reverse osmosis permeate, hereafter referred to as RO-permeate, is conveyed to a feed tank and its At least a portion can be used as a diluent during actual resin synthesis.

The UF-permeate is treated in a reverse osmosis membrane device, and some of the water contained in it is removed. to suitably form a solution having a dry content of at least 25% by weight. I can do it. A suitable temperature for reverse osmosis is about 30-50°C and a pressure of about 20°C. ~BObar is appropriate. The membrane of the reverse osmosis device is made of composite film material or Suitably composed of polybenzimidacylon or cellulose acetate.

When using the method of the invention with formaldehyde-based resins, an ultrafiltration step It is possible and advantageous to add formaldehyde binders to the feed to . This addition is carried out to further reduce the formaldehyde content in the final product. Ru. UF to bind more formaldehyde to the RO-enriched product - It is also advantageous to add a formaldehyde binder to the permeate. In this way , the total free formaldehyde load in the product and process is further reduced. Ho Urine where the lumaldehyde binder forms dimethylol urea with formaldehyde It is preferable that it is pure.

The present invention also provides a polymerization reactor, a 1M device for fractionation and purification of water-soluble synthetic resins. and a second membrane device for improving the permeate from this separation; The permeate outlet of the first membrane device is connected to the second membrane device via the supply tank. Also related to runt.

Polymer synthesis plant according to a preferred embodiment of the invention, comprising two separation devices Below is a schematic flowchart of such a plant. This will be described in detail with reference to the accompanying drawings showing the figure.

The plant includes a reactor 1 for the synthesis of water-soluble polymers.

The reactor is connected to a feed tank 2. Tubes 3 and 4 from supply tank 2 lead to ultrafiltration device 5 It leads to Removing the high molecular weight fraction from the concentrate side of the apparatus (denoted by C) , i.e. the concentrate can be passed through tube 6 to the feed tank for subsequent ultrafiltration. Return to step 2. The permeate side of the ultrafiltration device (indicated by P) is connected to the second supply tank 7. The second supply tank 7 is then connected to a second membrane device or reverse osmosis device by means of pipes 8 and 9. Connect to position 10. The permeate side of the reverse osmosis device is connected to the supply tank 2 via pipe 12a. can be connected to a wastewater treatment plant via pipe 12b; The condensate side is connected to the feed tank 7 via a pipe 11 and connected to the reactor by a valve 15 and a pipe 16. Connect to 1. High molecular weight product from feed tank 2 is passed to line 3, valve 13 and line 14. Therefore, it is obtained. Raw materials for resin synthesis are charged into the reactor 1 via a pipe 17.

The actual synthesis of water-soluble synthetic resins is a batch process, but processes other than polymerization are planned. can be operated continuously.

the necessary storage present between the device 5 and the tank 7, e.g. connected to the pipes 6 and 12; Tanks are not shown on the drawings.

According to the drawings, the plant is arranged to operate as follows, but other methods are also possible: As mentioned above, it is possible. Synthetic water-soluble resin with a wide range of molecular weight distribution is processed into a reactor. 1 and introduced into the supply tank 2. Add water to supply tank 2. supply The solution from tank 2 is passed through ultrafiltration device 5 where it is divided into two solutions. To separate.

The permeate solution containing water, low molecular weight polymers, unreacted monomers and by-products is passed through the membrane. and is led to the second supply tank 7 as shown in the drawing. At low resolution, this transparency The supersolution can be led directly to the reactor. Most of the solution is on the inlet side of the membrane, i.e. concentrated. Remains on the condensate side. Supply this solution again to the tank to increase its concentration. along the surface of the ultrafiltration device membrane by a pump (not shown in the drawing). can be made to flow. If the solution is treated in this way for a certain period of time, A concentrated solution of the product, the preferred high molecular weight polymer, is supplied by tubes 3 and 14. Remove from tank.

The permeate obtained from the ultrafiltration membrane device and collected in the second supply tank 7 is transferred to the second membrane device. Bring to 100 ml and concentrate by reverse osmosis. UF-Permeate concentrate is recirculated for a certain period of time. The system is ringed and allowed to flow along the membrane of the device, allowing the desired amount of water to pass through. reverse osmosis equipment The final concentrate from is then returned to the reactor via tubes 8 and 15 for new production of resin. used as a raw material for 211th! The solution passing through the membrane of the device is mainly It consists of water, part of which is reused in the polymerization process.

The invention is illustrated by the following examples, which are not intended to limit the invention. I will explain further. Parts and percentages refer to parts by weight and percentages by weight, respectively, unless otherwise specified. means.

Example 1 Water-soluble cationic urea-formaldehyde resin is added to a solution concentration of 23% dry weight. diluted with water until Transfer 55.2 kg of this solution to a UF-ps-20 type membrane, i.e. It was concentrated using an ultrafiltration device equipped with a polysulfone membrane. A solution with a concentration of 37.9% was obtained. The solution was passed through an ultrafiltration plant until

The amount of concentrated solution was 28.2 kg. The permeate, i.e. the dry content of the membrane passed through the membrane, 1 27.6 kg of solution with 0% was collected.

In this way, a dry amount of 2.64 kg of resin was separated from the initial amount of 12.6 kg. Enter The mouth pressure was 10 bar, the temperature was 40°C, and the filtration was carried out for 3 hours.

The amount of free formaldehyde in the initial product was 8.85% based on the dry weight of the resin. . That is, it was 0.87 kg in 55.2 kg of solution. Free formua in concentrate The amount of aldehyde was 4.1% based on the dry weight of the resin, or 0.41 kg, and the permeate The amount of free formaldehyde in the fish was 19.1% on a dry weight basis, or 0.53 fins. Ta. Difference between the total measured amount of formaldehyde 0.94 kg and the added amount 0.87 kg This is explained by the slight hydrolysis of the resin in the filtration membrane.

Example 2 Add water-soluble cationic urea-formaldehyde resin to a concentration of 8.1% dry weight. Diluted with water. 88.8) cg of this solution was filtered through an ultrafiltration device containing a polysulfone membrane. Concentrated. The solution was passed through an ultrafiltration device until a solution with a concentration of 20.4% was obtained.

The amount of concentrated solution obtained was 20.8 kg, or 4.2 kg of dry resin. membrane 48.2 kg of permeate solution having a dry content of 2.8% or a dry weight of 1.3 5 kg was separated from the initial amount of 5.8 kg. Filtration was carried out for 1.5 hours.

The total amount of free formaldehyde added was 0.390 kg, of which 0.23 0 kg was detected in the concentrate and 0.171 kg in the permeate. tree On a dry weight basis, the concentrate contains free formal It contained 5.47% dehyde and the permeate contained 12.7%.

Example 3 Example 2 was repeated using 83.0 kg of resin solution containing 8.9% dry weight. 4 Concentrate 24.2 with a dry content of 23.4% after 2 hours at 0° C. and 1 Obar kg and 58.8) cg of permeate containing a dry content of 2.95%. free hole After adding 0.510 cg of maldehyde, 0.280 cg was detected in the concentrated solution, 0.241 kg was detected in the permeate. 6 in the initial product on a dry weight basis of resin. ．． The concentrate contains 4.9% free formaldehyde compared to the 9% content, and the permeate contains 4.9% free formaldehyde. contained 13.9% free formaldehyde.

Example 4 The concentrated resin from Example 1 was used as a lubricating paper strength agent in a pilot paper machine. There was a strike. The valve is made of 50% bleached softwood and 50% 24” SR hard water. there were.

pH was 4.5.

Initial period 0.5 0.93 13.7 3.0 1.63 19.7 Concentrate 0.5 1.0B 15.4 Obtained after repeating Example 1 several times with a dry content of 8.8% or 4.92 kg. 55.8 kg of permeate solution, which is a mixture of permeate solution, was loaded into a filtration device for reverse osmosis. I entered. A thin composite membrane was used. The process was carried out at 40 bar% at 40°C. It was carried out for an hour. RO- with a dry content of 23.0% or 4.78 kg of dry resin. Containing 20.8 kg of concentrate and a dry content of 0.2%, i.e. 0.07 kg of dry resin. 4.78 kg of RO-permeate was collected.

The total amount of free formaldehyde added was 0.930 kg, of which 0.41 3) cg was detected in the RO-concentrate and 0.532 g was detected in the RO-permeate. It was done.

The synthesis of urea-formaldehyde resin uses RO-concentrate as one of the raw materials. It was carried out. Other urea and formaldehyde and other according to standard formulation method ingredients were added. The amount of RO-concentrate was 20% dry weight of the total dry weight added.

The product obtained had standard properties and showed good wet strength results.

Example 6 81.6) cg of the permeate solution having a dry content of 8.6% or a dry weight of 5.3 kg. Added to RO-filtration device. A thin composite membrane was used. The process is 40bar, It was carried out for 2.5 hours at 40°C.

19.0 kg of RO-concentrate with a dry content of 25% or 4.8 kg of dry resin and an RO-permeate containing a dry content of 1.17% or a dry weight of 0.5 kg. Obtained.

This RO-concentrate was used as starting material for a new synthesis. Added for new synthesis Approximately 24% of the total chemical added was from the RO-concentrate. new resin had standard properties and showed good wet strength results.

Example 7 Anionic urea-formal containing sulfur molecules with a dry weight of 21% or 7.8 kg 37.1 kg of the dehyde resin solution was passed through an ultrafiltration device. 10bar, 40 After 4 hours at a temperature of °C, concentration of dry content 29.4% or 6.70 kg 22 J kg of solution and 14.3 kg of permeate with a dry content of 7.6% or 1.1 kg was obtained.

Approximately 30% of the added sulfur groups are unfavorable as they adversely affect the final wet strength effect of the resin. It became part of the monomer by-products.

The total amount of sulfur-containing monomers added was 0.122 kg.

The concentrate contains sulfur-containing monomers o, oe kg, and the permeate contains Q, 082 kg. I was reading. Based on the dry weight of the resin, the initial product is 1.56%, the concentrate is 0.89%, The permeate contained 5.6%.

These products also undergo formaldehyde release from cellulose fibers according to standard methods. I tested it for output.

μg/mg dry weight Initial product 92 Example 8 Free formaldehyde addition added to stock with urea-formaldehyde resin The relationship between the amount of formaldehyde and the amount of formaldehyde released into the dry air of the paper machine was Tested on standard equipment.

The Hakusui system was completely closed, and the test was conducted under current conditions.

Wet paper strength to stock in air Enhancer 11iIcH20C1 (20 measured addition amount C) 120 addition amount PPm 2.0 55 0.81 2.4 HO, 9G The same urea-formaldehyde resins were tested except for their different free aldehyde contents. I did it. Product A contains 7.14% free formaldehyde on a dry basis of resin; Product B contained 2.25% free formaldehyde on a dry basis of resin.

Dry amount Free + 11cH20* CH20* Actual amount Product Added amount Added amount White water Medium air% ig/win ppm ppm A 2.44 55.8 43 1.08B 2.50 17.5 15 0. 41*CH2O: Formaldehyde ↓ Copy and translation of written amendment) Submission (Article 184-8 of the Patent Law) July 19, 1989 Yoshi, Commissioner of the Patent Office 1) Takeshi Moon 1. International application number PCT/5E87100637 2. Name of the invention Synthetic water-soluble polymer separation method and plant 3, patent applicant Address: Box 115, Nis-10061 Stockholm, Sweden 50 Names Cask Nobel Akcebolag Representative Zaid Shawl de (Nationality) Sweden 4. Agent〒105 Address: 2-8-1 Toranomon, Minato-ku, Tokyo → The scope of the claims 1. In the method for separating and reusing synthetic water-soluble resin, an aqueous solution of water-soluble synthetic resin is charged into an ultrafiltration membrane device, where two types of solutions, mainly high molecular weight ones, are separated. Concentrated liquid containing polymer molecules with low molecular weight, monomers with low molecular weight and a permeate containing by-products, and then the permeate is polymerized for repolymerization. A method characterized by recycling into the process.

2 The concentrate from the ultrafiltration device is recirculated to the same ultrafiltration device via the supply tank. and passing through the same device several times until a desired concentration is obtained. The method described in l.

8. Claim 1 or 2, characterized in that the permeate is improved before being recycled. the method of.

4. Perform reverse osmosis on the permeate and recycle the concentrated liquid obtained after reverse osmosis into the polymerization process. 4. A method according to claim 3, characterized in that it is circulated.

5. A claim characterized in that the synthetic water-soluble resin is a formaldehyde-based resin. 5. The method according to any one of claims 1 to 4.

6. The resin according to claim 5, wherein the resin is a urea-formaldehyde resin. Method.

7. Adding a formaldehyde binder to the aqueous solution charged to the ultrafiltration membrane device 7. A method according to claim 5 or 6, characterized in that:

8. A method characterized by adding a formaldehyde binder to the permeate for reverse osmosis. The method according to claim 5.6 or 7.

9. Includes a polymerization reactor (1) and an ultrafiltration membrane device (5), and permeation of the ultrafiltration membrane device Separation and production of synthetic water-soluble resin characterized by a liquid outlet connected to a polymerization reactor A plant for construction.

10. It further includes a reverse osmosis membrane device (lO), and the filtrate outlet of the ultrafiltration membrane device is a reverse osmosis membrane device. The permeate outlet of the reverse osmosis device is connected to the polymerization reactor. 10. The plant according to claim 9, wherein the plant is characterized by:

international search report

Claims (1)

[Claims] 1. In the separation and reuse method of synthetic water-soluble resin, an aqueous solution of water-soluble synthetic resin is charged into an ultrafiltration membrane device, where two types of solutions, mainly high molecular weight ones, are separated. Concentrated liquid containing polymer molecules with low molecular weight, monomers with low molecular weight and a permeate containing by-products, and then the permeate is recycled to the polymerization process. A method characterized by: 2 The concentrate from the ultrafiltration device is recirculated to the same ultrafiltration device via the supply tank. , passing through the same device several times until a desired concentration is obtained. Method described. 3. Claim 1 or 2, characterized in that the permeate is modified before being recycled. the method of. 4. Perform reverse osmosis on the permeate and recycle the concentrated liquid obtained after reverse osmosis into the polymerization process. 4. A method according to claim 3, characterized in that it is circulated. 5. A claim characterized in that the synthetic water-soluble resin is a formaldehyde-based resin. 5. The method according to any one of claims 1 to 4. 6. 6. The method according to claim 5, wherein the resin is a urea-formaldehyde resin. Method. 7. Adding a formaldehyde binder to the aqueous solution charged to the ultrafiltration membrane device 7. A method according to claim 5 or 6, characterized in that: 8. A method characterized in that a formaldehyde binder is added to the permeate for reverse osmosis. The method according to claim 5, 6 or 7. 9. It includes a polymerization reactor (1) and an ultrafiltration membrane device (5), and the permeation of the ultrafiltration membrane device Separation and production of synthetic water-soluble resin characterized by a liquid outlet connected to a polymerization reactor A plant for construction. 10. It further includes a reverse osmosis membrane device (10), and the filtrate outlet of the ultrafiltration membrane device is a reverse osmosis membrane device. The permeate outlet of the reverse osmosis device is connected to the polymerization reactor. 10. The plant according to claim 9, wherein the plant is characterized by: